Răspuns:
1.
2x-3y=5
-2x-2y=-20
_________ +
/ -5y = -15 =>y=3 =>x=7
2.
15x+20y=-30
-15x+21y=-93
___________ +
/ 41y = -123 =>y=(-3) =>x=2
3.
9x+3y=15
2x-3y=-4
________ +
11x / = 11 =>x=1 =>y=2
4.
x-1 < 3(7+x) ; x-1 < 21+3x ; -2x < 22 =>x > -11
4x-5x >_ -1-3 ; -x >_ -4 =>x <_ 4
=>sol. {-10, -9, -8, ..., 4}
5.
x <_ 3
2x-3x <_ -2-1 ; -x <_ -3 =>x >_ 3
=>sol.3
